Most likely the usual suspects.
Crud in the rigid hose from the front of sump to metering unit on the lhs, crud in that unit and crud in the top left of the water matrix; the air break.
You will need to remove the l/h panel, the door outer panel and the panel below the door to gain access to all parts in question.
Problem hopefully solved – crud in the sump outlet.
If anyone else has this problem, I managed to clear it using a bike pump, some garden watering system hose, insulation tape and the nozel from a tube of flexible sealant. Just connect it all up and blow air through the small outlet of the sump.
trackie wrote:……….I managed to clear it using a bike pump, some garden watering system hose, insulation tape and the nozel from a tube of flexible sealant.
Sounds like a night in for me that 😯 😆
Glad you sorted 😉